Among men infected with Zika while visiting the Americas, the median time the virus remained after being detected in their semen was nearly three months, a study of infected travelers returning to Belgium has found. Zika was found in semen samples from nine of 15 men who participated in the study, including in the semen of one participant who had had a vasectomy, according to a report published by the World Health Organization.
The longest period that Zika was found to have remained in detectable in semen was 144 days, the report shows. The report notes that persistence of the virus in semen appears common, and may be more common than estimated earlier, with a median time between symptom onset and semen testing of 23 days allowing time for the virus to clear among some men. The participants in the study had traveled to countries that included Venezuela, Haiti, Guadeloupe, Belize, Guatemala, Nicaragua, the Dominican Republic, Cuba, Jamaica, Mexico, Aruba and Curaçao.
While sexual transmission alone is unlikely to drive or sustain an outbreak of the virus where the mosquito that transmits it is not prevalent, it is likely to be the major transmission route of the virus, which can cause profound neurological birth defects as well as the paralyzing Guillain Barre syndrome, in those areas. The authors recommend that the semen of returning male travelers who are confirmed to have been infected be tested, and advised WHO and CDC guidelines pertaining to protecting sexual partners from the virus, including through condoms and abstaining from sex until the virus is found to have been cleared.